1. Field of the Invention
The invention relates to thin film deposition, and in particular to a vacuum coating apparatus and a coating method using the same.
2. Description of the Related Art
Conventional physical vapor deposition (PVD) technology, such as thermal evaporation, e-beam evaporation, sputtering, or molecular beam epitaxy (MBE), has been utilized for thin film coating. Laser induced high current pulsed arc (LIHCPA) is a currently developed multi-functional coating technology. Unlike conventional PVD and chemical vapor deposition (CVD) technologies, the LIHCPA technology is the only coating method using a pulsed laser beam emitted into excited material (i.e. target material) from the outside of a vacuum chamber and using a pulsed arc discharge device to generate high kinetic energy particles, thus allowing various gases with high concentrations to be filled into the vacuum chamber for thin film growth. This coating technology can be applied in fabrication of high quality thin films of any single-element or compounds of amorphous, polycrystalline, and epitaxial materials.
The principal of LIHCPA technology is that a laser beam is shifted along the surface of the target material so as to induce several tiny plasma regions. Combined with a high power pulsed arc design, the pulsed laser can perform high energy ionic plasma deposition. The laser beam can scan along a vertical direction (z-direction) via a step motor, such that the range for film-forming can be increased to more than 20 cm. When the laser beam is focused on the cathode target, the anode may induce tiny plasma regions on the surface of the cathode. According to the charge and discharge mechanism of the capacitor, a pulsed current of several kiloamps (kA) can be generated during discharge, thereby inducing high energy plasma in the vacuum chamber. This high energy plasma is able to generate highly ionized with high ion kinetic energy from the target. Thus, it helps to reduce deposition temperature and surface roughness of the thin film. Moreover, since thin film deposition/coating can be performed at room temperature, flexible substrates are not damaged during the process.
However, when LIHCPA technology is used to coat a film of increased thickness or of a non-conductive material, the anode surface may be contaminated by plasma because of the long thin film deposition time. Consequently, the conductivity of the anode surface is reduced, which makes it difficult to form plasma on the cathode target by arc discharge, and the deposition thickness of the film is greatly decreased. Thus, there is a need for a better apparatus and a more effective method to produce a film of considerable thickness.